In the retail industry, flat bed, laser-based readers, also known as horizontal slot scanners, have been used to electro-optically read one-dimensional bar code symbols, particularly of the Universal Product Code (UPC) type, at point-of-transaction checkout systems in supermarkets, warehouse clubs, department stores, and other kinds of retailers for many years. As exemplified by U.S. Pat. No. 5,059,779; No. 5,124,539 and No. 5,200,599, a single, horizontal window is set flush with, and built into, a horizontal countertop of the system. Products to be purchased bear identifying symbols and are typically slid by a clerk across the horizontal window through which a multitude of scan lines is projected in a generally upwards direction. When at least one of the scan lines sweeps over a symbol associated with a product, the symbol is processed and read. The multitude of scan lines is typically generated by a scan pattern generator which includes a laser for emitting a laser beam at a mirrored component mounted on a shaft for rotation by a motor about an axis. A plurality of stationary mirrors is arranged about the axis. As the mirrored component turns, the laser beam is successively reflected onto the stationary mirrors for reflection therefrom through the horizontal window as a scan pattern of the scan lines.
It is also known to provide a checkout system not only with a generally horizontal window, but also with an upright or generally vertical window that faces the clerk at the system. The upright window is oriented generally perpendicularly to the horizontal window, or is slightly rearwardly or forwardly inclined. The laser scan pattern generator within this dual window or bi-optical terminal or workstation also projects the multitude of scan lines in a generally outward direction through the upright window toward the clerk. The generator for the upright window can be the same as, or different from, the generator for the horizontal window. The clerk slides the products past either window, e.g., from right to left, or from left to right, or diagonally, in a “swipe” mode. Alternatively, the clerk merely presents the symbol on the product to a central region of either window in a “presentation” mode. The choice depends on clerk preference or on the layout of the system.
Sometimes, the upright window is not built into the system as a permanent installation. Instead, a vertical slot scanner is configured as a portable reader that is placed on the countertop of an existing horizontal slot scanner in a hands-free mode of operation. In the frequent event that large, heavy, or bulky products, which cannot easily be brought to the reader, have symbols that are required to be read, then the clerk may also manually grasp the portable reader and lift it off, and remove it from, the countertop for reading the symbols in a handheld mode of operation.
As advantageous as these laser-based, point-of-transaction systems have been in processing transactions involving products associated with one-dimensional symbols, each having a row of bars and spaces spaced apart along one direction, these systems cannot process stacked symbols, such as Code 49 that introduced the concept of vertically stacking a plurality of rows of bar and space patterns in a single symbol, as described in U.S. Pat. No. 4,794,239, or two-dimensional symbols, such as PDF417 that increased the amount of data that could be represented or stored on a given amount of surface area, as described in U.S. Pat. No. 5,304,786. Both one- and two-dimensional symbols, as well as stacked symbols, can be read by employing imaging readers each having a solid-state imager which has a one- or two-dimensional array of cells or photosensors that correspond to image elements or pixels in a field of view of the imager. Such an imager may include a one- or two-dimensional charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS) device, as well as associated circuits for producing electronic signals corresponding to the one- or two-dimensional array of pixel information over the field of view.
It is therefore known to use a solid-state imager for capturing a monochrome image of a symbol as, for example, disclosed in U.S. Pat. No. 5,703,349. It is also known to use a solid-state imager with multiple buried channels for capturing a full color image of a symbol as, for example, disclosed in U.S. Pat. No. 4,613,895. It is common to provide a two-dimensional CCD with a 640×480 resolution commonly found in VGA monitors, although other resolution sizes are possible.
It is also known to install the solid-state imager, analogous to that conventionally used in a consumer digital camera, in a bi-optical, dual window, point-of-transaction workstation, as disclosed in U.S. Pat. No. 7,191,947, in which the dual use of both the solid-state imager and the laser scan pattern generator in the same workstation is disclosed. The workstation is typically either mounted on the countertop, or is seated into a well formed in the countertop. The horizontal and upright windows are typically set flush with, and built into, the workstation. It is possible to replace all of the laser scan pattern generators with solid-state imagers in order to improve reliability and to enable the reading of two-dimensional and stacked symbols, as well as the imaging of other non-symbols or targets, such as signatures, driver's licenses, receipts, etc. It is also known, for example, as disclosed in U.S. Pat. No. 7,748,631, to arrange a plurality of stationary field minors within the workstation to capture return light from the symbol through either the horizontal and/or the upright window over intersecting fields of view. The captured return light is successively reflected onto the stationary field mirrors for reflection therefrom to at least one solid-state imager.
As advantageous as the known imager-based, bi-optical workstation has been in processing products, the flush-mounted, upright window tends to get scratched by products scraping the upright window and/or contaminated by dirt, dust, finger oil, food particles and like contaminants that are deposited during normal use in either the swipe and/or presentation modes of operation. Such scratching often occurs by inattentive clerks. Such contamination is inevitable, especially in retail and warehouse environments. Depending on their extent, such scratching and contamination eventually obscure the return light and degrade reading performance. Hence, the flush-mounted, upright window requires frequent cleaning and, in extreme cases, the heavily scratched window requires repair and replacement. Cleaning of a contaminated window, however, may not be regularly or adequately performed. Repair and replacement of a scratched window puts the workstation out of service.
To attempt to alleviate such window scratching and contamination, it is known to slightly recess the upright window in the workstation. However, such recessing is marginal, that is, on the order of three-tenths of an inch and less. Even so, many products passed by the marginally recessed upright window often scrape the upright window, especially when the products are in bags or like yieldable containers that project into such marginal recess as they are swiped past the upright window during check-out.
Accordingly, a solution is needed that eliminates the inconvenience and minimizes the expense of cleaning, repairing and replacing the upright window of the bi-optical workstation. A means of protecting the upright window is thus needed.